Reclaiming rubber with bis (trialkyl phenol) sulfides



Patented July 29, 1952 PHENOL) SULFIDES Harry E. Albert, Akron, Ohio, assignor to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio N Drawing. Application June 7, 1947, Serial No. 753,361. In Canada November 22, 1946 This application is a continuation-in-part of my copending application Serial No. 643,828, filed January 26, 1946, and matured into U. S.

=-This invention relates to the reclaiming of vulcanizate's of both natural and synthetic rubbers;

with a softening and swelling agent composed at least in part of a bis(trialkylphenol) sulfide of the-formula:

-bis(3,4,6-trialkylphenol) sulfides and particular ly the bis(4,6 dialkyl m-cresol) sulfides are preferred.

The bis(trialkylphenol) sulfides are preferably prepared by reacting a suitable phenol witha sulfur chloride in an inert solvent, such as'ca'rbon tetrachloride, ethylene dichloride, etc. To,

obtaincompounds where as in the above generali formula equals 3 or 4, free sulfur may be added to the reaction mixture. The solvent may be" The reclaiming is effected by heating the vulcanizate at a temperature of at least 300 F.

6 Claims. (Cl. 260-23) omitted, and the mixture may be heated.,-;The.

preferred treating agents are monosulfides or disulfides. They are advantageously prepared by reacting the ,phenolwith sulfur monochloride withio'r without heating. ,This general-react n.

is known; The bi's(trialkylphenol) sulfides .may be prepared by reacting sulfur monochloride or sulfur dichloride withfa phenol, such as: a H

- 2 3-methyl-4-tert-butyl-S-methylphenol 2,3edimethyll-butylphenol v In each of these phenols at least one ortho or para position is open and available for reaction with the sulfur chloride.

The bis(trialkylphenol) sulfide may be used alone or with other softening or swelling agent's.

It has been found that in alkaline solutions bis(trialkylphenol) sulfides do not soften the vulcanizate to the extent that they do in neutral or slightly acidic solutions so that the latter are preferred. There appears to be a chemical reaction between the rubber and at least some of the bis(tria1kylphenol) sulfide. If as little as 3 per cent on the weight of the vvulcanizate'is used, there'action appears to'be catalytic. Using temperatures as high as 600 F., one obtains increased activity in the treatment'of GR-S vulcanizateif as little. as, V2 per cent of one of the bis(triall:ylphenol) sulfides of this invention (based on the weight of the vulcanizate) is added to any of the usualsoftening' and swelling compo sitions. At lower temperatures of about 300 F., as little as 0.5 to 1.0 per cent" gives a quite noticeable effect. With GR-S inner-tubestock; for example, as little as 1,0 per cent at such lower temperatures gives noticeable chemical softening. The bis(trialkylphenol) sulfides are much more active on natural rubber than-GR-S, and as little as 0.1 per cent has a noticeable effect on natural rubber vulcanizate. in the scrap rubber, it is desirable to use a cellulose hydrolyzing agent along with the chemical softener.

Swelling agents,, such as, crude solvent naphtha, refined solvent naphtha, petroleum naphtha, turpentine, dipentene, cymene, etc., may beaddedto the bis'(trialky1phen0l) sulfide prior touse in order to swell the rubber; This aids the catalytic reclaiming action; Softening. agents', such as asphalt, pine tar, mineral rub-, .ber; medium process oil, rosin, coumarone resins,

rosin.,oil, etc;, may be used in the reclaiming process:- with the bis(trialkylphenol)' sulfide. Some of these introduce tack into the reclaim in addition to softening the vulcanizate. Less total softening or swelling agent is required when areclaiming agent of this invention is present.

In using oneof the bis (trialkylphenol) sulfides of the present invention on a vulcanizate of nat- If fiber is present like polymerized chloroprene (neoprenes), a rub 19 -1;

ber-like copolymer of isobutylenexand: aiismalls amount of butadiene-L3 or isoprene (Butyl:rub'-.- ber), a rubber-like copolymer of butadiene-lfi, and styrene (GR-S) or acrylonitrile (Buna.N)j;

etc., or mixtures of these with themselves andrj natural rubber.

Thefollowing examples are illustrative:

EXAMPLES l-3 Three batches for pan-heater treatment were 20 prepared, each-containing 100.parts of GRS No. 1 peeli'ngs (preparedfrom vulcanized-,GR-S scrap) ground to 5.mesh.'- The reclaiming agent was composed of 3 partssdipolymer oil (more.-

accurately termed an aromatic -hydrocarbon.dis.-. Q5

tillate consisting of mixed polymers of'coumarone and-.indene resins in. liquid form), 5-parts pinetaroil-,5 5-parts dipentene; 2 parts .-rosin, .and,- for therrespeetive batches:

Example-1: Z parts diphenol disulfide e Example 2: 2 parts bis(-o-'cresol) disulfide- Example 3: 2 "parts bis (4,6-'di-tert+butyl m ore-- sol) disulfidej Each.. batch. was separately, mixed minutes ineassuitablemixerand -then-cooked .4 hours at 175. lb.-/sq.. in.-.steam:pressure (3'Z8 .'F.)."ina; pan. heater.. The batches-were then. subjected. tor. vacuum for. 1 -.hou-r,- massed; and-then .refined.

three :passes --on: .a tight,;- cool .mil-l. The,.stock.. 4

thicknesssof each is givlen in' inchesinthe-fol; lowinggtable; Sheet thickness is a ,measurewoi; softnessor plasticity the thinner the sheet, the... greater the activitymf the softening agents.v Examples 1-and=2:.do .not:come within the.=scope.- of the appended claims, comparison.

- Table.- I.

" Thickness 1; Comments Dry; With5cnlyriair bodyhnd'a little tack; In general, not satisfactory. Dry. Poor tack; In'gcneraknctsatisfactory. 'Vcrygood body and goodtackv .Ver'y :goodr:

Work-ability. l

V l V EXAMPLEs -m 7 Four batches of IQO' parts-each'; of 5=mesh" vulcanized GR-S tire scrap (containing-fabric) weretveighed out. Tol each of these (exceptg 60 the one-which wasused as-a control) "was added 1 one of the followingreclaimed mixtures but are added... fen/ were i prepared by mixing a about Q-IO parts of:

dipolymerpil; fi parts wood rosin, 200 parts 1? per cent'zine chloride solutiom'and the follo'w' ingzreagentsz I r r Examples: Nothinga Examplefi 1.5. parts.-diphenol sulfide Example .6 11 1.5 parts :di(ocreso1') disulfide-:-

Examplefl 1.5 parts ibis (4,6-di ,tertbutylemr-ere'- 7O Eah1batch washeated'in a digester. for.8hours at 17 5;;'lb./sq;.;in. steam'pressure (378 F.) and by three passes through a tight mill.

Example The following table records the results, the sheet thickness being recorded in inches:

Table II Comments v Very dry and lacy with no tack. Very poor body. Not satisfactory.

Extremely poor sheet. Not satisfactory.

.. Lacy with practically no body or tack. Not

satisfactory.

Very good body with good tack. Good workability.

The*reclaJimingagents of Examples 4, 5, and 6 do not-comewithinthe scope of the invention and;ar.e included foncomparison.

EXAMPLE 8 GR-S passenger tires were ground to pass through a 5-mesh screen. The mix was preparedas follower; l

. a Partst GR-S tire scrap .(mesh). 10.0.: Crude solvent naphtha 8.5 i Wood-rosin" 6.5 Bis(4,6edietert butyl-macresol); dis'ulfide:.- 1:5

1%? zinc2:chlo'rid'e: 2001 9 The tbatchiwas. heatedin a 1 factory digester :58 hours .at- 175 ,lbs./sq.;in-. steam. pressure (378:- Fr). v dumped,'washed, and dried. Two hundredand'? fifty pounds of the mix were massed for 10 minutes on an 84-inch mill. This was then refined, strained through a ZZ- mesh screen, and refined in the iactory.- The-stock ran very clean with practically no. .tailings,\had very good body and tack, and wasvery soft.

EXAMPLEZ. 9:

This factory batchi'was "made up as follows I.

' Parts bygweight GPA-1S ,No.. 1 .peels. (5=mesh) 100.1. .1 Crude solvent naphthae u 8* Wood-rosin.- r, f Bis.(-4,6,-.di-tertebutykmrcresoli-- diS1-l1f1de: --1.'5

Theingredients were mixed, loadedintopans, cooked '4 hours. at 175. lbs/sq. in". steam .pressure (378 "F.) iniactory. pan heatersnanddhen suh. jected 'to vacuum. for 1 hour. The stock was. massed; refined, strained ,jthrough... a... 22e'meshscreen; and refined in the .factory. The stockmassed well, ,ran very well; smooth... sot',.. and;- had. -good .body; and tack; It. strained satis=.

factorily;

EXAMPLE. 10

The" vu1canizate"of, .this example was butyl rubber which had been cured with quinone' dioxime or quinonedioxime dibenzoate. known' as-GMF and GMF "dibenzoate cures). The. rubber was ground" to" pass a. r5v-meshiscreen.

One hundred parts of "this were heated for '8 hours at 378 F. withf5'parts of -a.-.20=- percent solution of bis(4,6- diatertebutyl mecresoh. disulfide in high-boiling."hydrocarbon solvent in a factory pan devulcaniz'erizi The following treating bath was used:

v Parts b'y weight GMF cured butyl scrap. (5-mesh)- Crude solvent naphtha: 2' Wood rosin 2 Bis (4,6-di-tert butyl mecresol) disulfideir'u 1 The finished reclaimpossessed. fair.- 'body: -'and then'dumped, washed.dried, massed..and'frefinedQ75 good tack and good:workability.-

steam pressure in a factory digester.

EXAMPLE 11 The stock treated was black air ba s of natural rubber. These were cut to approximately A-inch mesh. I

The treating formula was: I

Parts Natural rubber (black air-bag scrap) 100 High-boiling petroleum distillate softener (Parafiux) 6 20% solution of bis(4,6-di-tert-butyl-mcresol) disulfide in high-boiling hydrocarbon solvent 1.5

The batch was heated in a pan heater for 5 hours at 330 F. The devulcanized biscuits were refined by two passes in the factory and possessed'fair body and tack with generally satisfactory workability.

EXAMPLE 12 The vulcanizate treated wasneoprene thread scrap. The petroleum softener and solution of chemical softener were the same as in the preceding example.

' Parts Scrap neoprene 100 Parafiux 40 20% solution of chemical softener 7.5 Wood rosin 5 The mixture was heated in a pan heater for 7 /2 hours at 330 F. The devulcanized biscuits were of good quality. Upon refining, the sheetpossessed good body and tack properties.

EXAMPLE 13 The stock of this example was peelings from bus and truck tires. As usual for such stock, thepeelings were high in carbon black. The solution of chemical softener was the same as in the two preceding examples.

Parts GR-S No. 1 giant peelings 100 Coal-tar naphtha 3 Wood rosin 2 20% solution of chemical softener 0.75

EXAMPLE 14 In carrying out this example, unsorted recapped passenger tires were reclaimed. The treating formula was:

. Parts Unsorted recapped passenger tires 100 Pine-tar oil 2.7

Wood rosin 3.3 Bis(4,6-ditert-butyl-m-cresol) disulfide 0.5 Water 200 Zinc chloride 2 The batch was cooked 9 hours at 175 pounds The resulting reclaim was found to have good properties of body and tackwith a thin sheet.

EXAMPLES 15 AND.16- I I GR-S tread scrap was ground to about 5 mesh and treated according to the following formulae:

Terpene hydrocarbon (B. P. 17320l 0.). Cumar 2% MH BisOi,fi-di-tert-butyl-m-cresol) disulfide Bis(2,3,5-trimethylphenol) disulfide.

Each batch was mixed 10 minutes and-then' cooked4 hours at 1'75 pounds steam pressure. It

was then treated under a vacuum 1 hour and refined by three passes through a cool mill. The reclaims formed thin sheets and had good'body and tack. Both reclaims had a Mooney plassulfides are generally useful in the reclaiming of vulcanizates at temperatures of 300 F. and above; Temperature and time of treatment will depend upon the nature of the stock, etc. In carrying out the reclaiming operations, the bis(trialkylphenol) sulfide may be introduced separately or in solution in a softening or swelling agent. The treating bath may be an aqueous emulsion in which the noncontinuous phase is a solution of the bis(trialkylphenol) sulfide. The concentration of bis(trialkylphenol) sulfide in the solution or other treating bath may be varied to suit the particular need of the scrap to be reclaimed. It may vary from 0.1 per cent to as high as per cent. Other softeners and treating agents, solvents, diluents, etc., may be employed as desired without departing from the invention which is defined in the claims which follow.

What I claim is:

1. The process of reclaiming a rubbery vulcanizate of the class consisting of vulcanizates of natural rubber, polymerized chloroprene, copolymer of isobutylene and a relatively small amount of a monomer of the class consisting of butadiene- 1,3 and isoprene, copolymer of butadiene-1,3 and styrene, copolymer of butadiene-1,3 and acrylonitrile, and mixtures thereof which comprises heating the same at a temperature of at least 300 F. with bis(4,6-di-tert-butyl-m-cresol) disulfide, sulfur of the sulfide being linked to the 2-position in the ring.

2. The process of reclaiming vulcanized, rubbery copolymer of butadiene-l,3 and styrene which comprises heating the same at a temperature of at least 300 F. with a bis(trialkylphenol) sulfide which has the formula:

where R1, R2 and R3 are alkyl groups each containing one to nine carbon atoms, the total number of carbon atoms in said alkyl groups is no more than twenty, x is 1 to 4, and in each aryl nucleus at least one of the positions ,ortho and para to the hydroxyl is unalkylated and linked to the sulfur.

3. The process of reclaiming vulcanized, rubbery copolymer of butadiene-1,3 and styrene which comprises heating the same at a temperature of at least 300 F. with a reclaiming agent 4 R1 I R1 where R1, R2 and R3 are alkyl groups containing one to nine carbon atoms, x is 1 to 4, and the totalnumber of carbon atoms in R1, R2 and R3 is no more than twenty.

4. The process of reclaiming vulcanized, rubbery copolymer of butadiene-LB and, styrene which comprises heatingthe same at a tempera ture of at 1east300'F. with a -bis'(-3,4,6-trialkylphenol) sulfide in which'one of 'the alkyl groupsis' methyl and the other two each contain one:

to-nine carbon'atoms, sulfur of the sulfidebeing linked to the 2-position in the-ring,

5.- The process of reclaiming vulcanized ,rubbery copolymer of 'butadiene-LZ; and styrene which comprises heating the'same at a temperature of atleast 30%) F; with a; bis(4,6-dialkyl-m cresollsulfide in which the groups designated 3 alkyl each contain onejitomine'carbon atoms, sulfur of the sulfide being linked to the 2 -position in the ring.

6. The process of reclaiming vulcanized',"rub'- bery copolymer of butadiene-1,3 and i 'styrene;

which comprises heating the same atatemperature of at least 300 F. with bis(4,6-di-tertbutyl UNITED STATES PA'IENTS Number Name Date 1,996,001 Seaman Mar. 26,- 1935 2,191,266 Williams Feb. 20, 1940 2,359,122 Kirby et a1 Sept. 26,- 1944' 2,363,873 Kirby et a1. Nov. 28, 1944 2,372,584 Kirby et a1 Mar. 27, 1945 2,402,448 Richards June 18, 1946 2,409,687' Rogers et al., 01:15:22, 1946 2,449,026 Van Gilder Sept; 7, 1948 2,495,145 Smith et al Jan. 1'7," 1950 

1. THE PROCESS OF RECLAIMING A RUBBERY VULCANIZATE OF THE CLASS CONSISTING OF VULCANIZATES OF NATURAL RUBBER, POLYMERIZED CHLOROPRENE, COPOLYMER OF ISOBUTYLENE AND A RELATIVELY SMALL AMOUNT OF A MONOMER OF THE CLASS CONSISTING OF BUTADIENE1,3 AND ISOPRENE, COPOLYMER OF BUTADIENE-1,3 AND STYRENE, COPOLYMER OF BUTADIENE-1,3 AND ACRYLONITRILE, AND MIXTURES THEREOF WHICH COMPRISES HEATING THE SAME AT A TEMPERATURE OF AT LEAST 300* F. WITH BIS(4,6-DI-TERT-BUTYL-M-CRESOL) DISULFIDE, SULFUR OF THE SULFIDE BEING LINKED TO THE 2-POSITION IN THE RING. 